Telephone system



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Jan. 16, 1923.

Patented Jan. 16, 1923.

UNITED fsrIATEs PATENT OFFICE. f

IIIRAM n culmina, or CHICAGO,` ILLINOIS, AssICNOa 'ro KELLOGG svvIrCIIBOAnD AND SUPPLY COMPANY, or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

TELEPHONE SYS'IElVlI.`

Application iiled July 18, 1918. Serial No. 245,446.

To all whom it may concer/a."

Be it known :that I, D.y Cunnmn, a citizen of the lUnited States 'of America, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of ywhich the following is a specification.

My invention Arelates tofrepeating coils or telephone transformers, and Lhas to. do more particularly with repeating coils of the non# ring :through type :such vas are :used'in cord circuits or link circuits for connecting` '1together the subscribers telephone lines [of a telephone exchange system. l

My present invention is .designed to prevent alternating currents of a ylow frequency from passing through repeating coiils from one side of the circuit to the other, .but offers no resistance whatever to thepassing through of alternating currents of ahigher frequency, such as talking currents. y

In magneto telephone systems, it is desirable to lhave double supervision, that is, to have one `supervisory device controlled by the calling subscriber and one controlled by Ithe called subscriber. A great deal Of trouble has been vencountered in providing double supervision of the character above described- Owing #to ,fthe Afact that the generator current sent in by either subscriber over his telephone line when signaling the operator, particularly when the subscribers line is a short one, not oniyoperates the subscribers own supervisory signal Abut also passes `through the repeating coil `the cord circuit and operates the other subscribers supervisory signal. Some attempts 'have been made to Overcome this undesirable feature but lthey have always ended withthe result thatthe eficiencyof the repeating coil for talking purposes has been greatly impaired to a practically uncommercial point, or the repeating coil would permit va small amount of ringingcurrent to passl through so that when the/supervisory device is adjnsted to work on a :weak l'current over a long A-line it will also work over a `short line by current transmittedthroug'h the repeatingcoil from the other end of the cord circuit. 'f

I :have arranged the windings of the :repeating coil Yof my -inventionfsofthat when currents of flow frequencies are. 'transmitted a :differential efetistobtained :upon the-cove of the repeating coil, but'when currents of higher frequencies yare transmitted, owing to Athe enormous impedance Offered by these windings to the talking-current, the repeating coil functions as two separate ,trans formers connected in series, -although they are located upon the same core. f

The above-mentioned features, as Well as others, will be more particularly pointed out in the ensuingspecification and inthe appended claims. i v Referring to my invention'as-illustated in the accompanying drawing lin which like i characters denote like parts,A v

Fig. 1 shows a complete circuit connection between a calling andA a calledsubscriber through the medium .of alink vcircuit provided with a repeating ycoil ofvmIy invention.

Fig. 2 shows how the windings of my repeating coilare connected; and i Fig. 3 shows the relative position of the windings of my repeating coil.1 f,

Referring to Fig., l, this circuitfirepre# sents kdiagrammatically a magneto substa-` tion A which terminates aty the'jcentral AeXf Change in line equipment L; ya calledysubstation B which terminates inline. equip.-

sok

ment L', and a ycord `:circuit Cforconnecting line A to line B. y f

The magneto substation A com-prises the usual talking equipmentand hand generator oiiice inthe usual drop D andf'jackJ.

The cord circuit C comprises/the usual answering plug AI andv calling plug CP vor magneto, and terminates in .the .central inductively'con-nected .together by means of f theltalkfing strands of the cord circuitf. An answering supervisory'deviceAS and a calling supervisory device CS. are furnished.vv .A `repeating coil RC is provided and .has four windings connected intermediate the, ends of the cord circuit, windings l yand .of

the cord circuit being connected `together through a condenserK, and windings Qtaiid 4f of the cord circuit lbeing connectedftogether through ithe condenser K',

An foperators itlepholxset O land he l usual ringing `and listening lkeys are )also provided. f. The .equipment of the substation B and .the line circuit L are the Simeffls the'equipment ofthe SubStzOl A.. and :111,19 circuit.- L.. i i i CII manner in which the windings of therepeating 'coil are connected. Winding l of 'the repeating coil extends around the core in one direction while winding 3, with which winding l connects, is wound around the core in the opposite direction, thereby causing the lines of force set up in the core of the repeating coil in one direction by one winding to be neutralized by the lines of force set up in the core of the coil by the other winding in the other direction when an impulse of current of a low frequency is passed through these windings. llindinge of the repeating coil, which is connected in series with winding 2 of the repeating coil, is also Wound around the core in the opposite direction to that of winding 2, so that one of these windings tends to neutralize the magnetic effect of the other of these windings when an impulse of low frequency current is passed through these windings.

Referring now to Fig. 3, the repeating coil or inductorium comprises aLl-shaped core X preferably marde of small lgauge Norway iron which is wrapped with tape to help keep its cylindrical form. The `core is made of smally gauge Norway iron to reduce the hysteresis loss to a minimum. The coil is made up of two spools Y and Z*i each spool having two windings namelyn an outside winding l and an inside winding 2 on spool Z, and an outside winding 4l and an inside winding 3 on spool Y.

The windings areconnected so that the inside winding of one spool is connected te the `outside winding of the opposite spooh and these two windings form one-half of the transformer circuit. This arrangement permits each half of the transformer circuit being in the same dimensional relation to the core. With this arrangement, which results in each half of the transformer circuit being in the same dimensional relation to the core, the current induced from one-half of the transformer to the other reacts on the core to the same degree as the impressed current with the result that transformation is obtained with the minimum loss.y

Owing to the fact that the core of the coil is comparatively short.; the lines of magnetism, built up by energizing one winding of a pair of windings have time to neutralize'the lines of force built up by the other winding of the pair of windings when the frequency of the current .is low, but when the frequency of the current is very rapid,l as is the frequency of talking current, the winding at each end of the core acts as a separate' transformer, the effect being like two transformers having their primaries and secondaries connected in series. If the core off/the coil should be extended to a great enough length then the ivinz-ilng'm1-eachrend-ofthe coretwould jackrfl 0f the calling line and inquires the wants of the calling subscriber. The operator next tests the line of the called for subscriber and completes the connection thereto, if the line is idle, b v connecting the p alling plug CP to the jack J of the called The subscribers now converse over the heavily marked conductors, and the repeating coil RC operates very efliciently to repeat the high frequency talking' current from one end of the cord circuit to the other. y

`When the subscribers are through tall:- ing7 they both operate their hand generators to operate their respective supervisory signals. The calling subscriber operating his hand generator operates the supervisory de vice AS, and the called subscriber operating his han d generator operates his'supervisory device CS. The low frequency generator current sent into ithe exchange from either the answering end of the cord circuit or from the calling end of the cord ci reuit does'not pass through the repeating coil BC andoperate the supervisory device at the other end of the cord circuit due to the differential action ef the coils upon the core of the coil RC when current of low frequency is sent through eitherk pair winflings of thc transformer.

lll/hilc the invention has been described with particl'llar reference to the details of construction, it should be understood that it is not limited thereto, as many changes and modifications may be made therein without departing therefrom, and I therefore wish to cover all such changes and modifications which come within thc spirit and scope of the appended claims.

hWhat I claim as new and desire to secure by United c ates Letters Patent isi l. in transformen U-shaped core composed of magnetic material having w' dings on the arms of said core7 said windlngs comprising two primary and two secondary windings, Vone primary and one secondary winding being mounted on one arm portion of thcicore and theotber primary and secondary windings being mounted upon the other arm portion of the core, the primary winding mounted on one arm portion of the core being an inside winding and connected to the primary winding mounted on the other arm portion of the core which is an outside winding, the two primary windings being wound in opposite directions, a supervisory signal connected -in bridge circuit between said primary windings, a condenser interposed between said primary windings for causing current to pass through said supervisory signal to operate the same, the secondary winding on one arm portion of the core which is an outside winding being connectedto the secondary winding on the other arm po-rtion of the core which is an 'inside winding, the two secondarywindings being also wound in opposite directions substantially for the reasons set forth, another supervisory signal connected in bridge circuit between said secondary windings, and a condenser interposed between said secondary windings for causing current to pass through said second supervisory signal to operate the same.

2. In a transformer, a U-shaped core composed of magnetic material hav-ing windings on the arms of said core, said windings comprising two primary and two secondary windings, one primary and one secondary winding being mounted on one arm portion of the core and the other primary and secondary windings being mounted upon they other arm portion of the core, the primary windingmounted on one arm portion of the core being an inside winding and connected to the primary winding mounted on the other arm portion of the core which is an outside winding, the two primary windings being wound in opposite directions so as to have a neutralizing effect upon the core of the transformer for a low frequency current but each set of windings functioning as a separate transformer for high frequency current, a supervisory signal connected in bridge circuit between said primary windings, a condenser for causing low frequency current to pass through said supervisory signal to operate the same, the secondary winding on one arm portion of the core which is an outside winding being connected to the secondary winding on the other arm VCook and State o-f Illinois this portion which is an inside winding, the two secondary windings being also wound in opposite directions substantially for the reasons set forth, another supervisory signal connected in branch circuit lbetween said i vsecondary windings, and a condenser interposed for causing -current of a low frequency to pass through said last supervisory signal to operate thev same.

3. A transformer of the character `described having a `U-shaped corel provided with two sets of two windings each, the inside winding of the lone set being connected to the outside winding of the other set. to form one-half of the transformer circuit, one of said windings being wound in a dextrorsal manner and the other of said windings being wound in a sinistrorsal manner,

the other two windings of the said two sets n -of said pairs of windings and the other signal connected in circuit between the other one of said pairs of windings, a condenser in series circuit with and between one of said pairs of windings, and 'a condenser in series circuit with and between said other pair of windings, said condensers permitting low frequency current to pass through saidsupervisory signals yto cause the operation of the same, said supervisory-signal being non-responsive to high frequency current. Y y

Signed by me at Chicago, inthe county of 15th day of July, 1918. 7

HIRAM D. comuna 

